1. Field of the Invention
The present invention relates to a battery pack, and more particularly, to a battery pack which can increase coupling force between a holder and a protection circuit board, and improve processability and productivity.
2. Description of the Related Art
Secondary batteries are rechargeable and can be repeatedly used. Thus, the secondary batteries are more economical than disposable batteries.
Also, the secondary batteries can realize high capacity with small volume, and thus are used as a driving power source for handheld electric devices such as mobile phones, MP3 players, notebook computers and digital cameras.
The secondary batteries are also used in high power products such as hybrid cars and electric tools as well as handheld electrical appliances.
The secondary batteries include, for example, nickel-cadmium batteries, nickel-zinc batteries, nickel-metal hydride batteries and lithium secondary batteries.
The lithium secondary batteries are widely used because they are compact, and provide high capacity, high operating voltages and high energy density per unit weight.
The lithium secondary batteries are formed by accommodating an electrode assembly and an electrolyte in a casing and sealing the casing, which is called a bare cell.
The lithium secondary batteries may be classified into a can type and a pouch type depending on the shape of the casing, and the can-type batteries may be classified into a square type and a cylindrical type.
The bare cell is electrically connected with a protection circuit board to prevent hazards caused by abnormal operations such as overcharge, overdischarge and overcurrent.
The protection circuit board is formed by mounting protection circuits such as a PTC thermistor, a protection circuit, a fuse and a temperature sensor on a printed circuit board.
The bare cell and the protection circuit board are formed in the shape of a battery pack, which may be a hard pack type in which the secondary battery and the protection circuit board are accommodated in a separate casing.
Or, the battery pack may be an inner pack type in which the protection circuit board is covered with a cover and the exterior is tubed and labeled.
The battery pack may include a fixing mechanism (hereinafter, a holder) between the bare cell and the protection circuit board, which has a specific shape capable of coupling the protection circuit board and can maintain a distance between the bare cell and the protection circuit board.
When the protection circuit board is coupled to the holder, a coupling protrusion formed on the holder is inserted into a coupling groove formed in the protection circuit board.
In fabrication of the protection circuit board and the holder, a size difference between the coupling protrusion and the coupling groove can occur due to assembly deviation.
However, since the coupling protrusion is formed in a prismatic shape having a fixed size in the conventional art, a mold may have to be adjusted to address the mismatch between the protrusion and groove.
Thus, an unnecessary process may have to be performed due to the mold adjustment thereby increasing manufacturing costs.